Monday 15 April 2013 04.00 EDT
First published on Monday 15 April 2013 04.00 EDT

There are some novels that tell a great story and others that make you change the way you look at the world. Chimamanda Ngozi Adichie's Americanah is a book that manages to do both.

It is ostensibly a love story – the tale of childhood sweethearts at school in Nigeria whose lives take different paths when they seek their fortunes in America and England – but it is also a brilliant dissection of modern attitudes to race, spanning three continents and touching on issues of identity, loss and loneliness.

This is Adichie's third and most ambitious novel – her first, Purple Hibiscus, was longlisted for the Booker prize and her second, Half a Yellow Sun, won the Orange prize. A highly acclaimed 2009 collection of short stories, The Thing Around Your Neck, cemented her position as one of the most promising African writers of her generation. She was awarded a prestigious MacArthur "Genius" grant and in 2010, the New Yorker featured her in its list of the 20 best authors under the age of 40.

So a lot is expected of her. Gratifyingly, Americanah does not disappoint. It tells the story of Ifemelu, a spirited young girl with strong opinions, and her teenage boyfriend, Obinze, who grow up with romanticised notions of the west, shaped by the literature of Graham Greene, Mark Twain and James Baldwin. When Ifemelu is presented with an opportunity to continue her postgraduate studies in Philadelphia, she takes it. Some years later, Obinze, too, goes in search of a better life, but to Britain.

It is at this point that Adichie really begins to flex her muscles as a novelist: the sense of dislocation felt by both characters in two countries with wholly different histories and class structures is expertly rendered. She has an extraordinary eye for the telling nuance of social interaction within a particular kind of liberal elite.

In England, Obinze struggles to get hold of the ever-elusive national security number that will enable him to work legally. The newspapers are full of stories about schools "swamped" by immigrant children and politicians' attempts to clamp down on asylum seekers. Against this backdrop, he is invited to a smug Islington lunch party by Emenike, a former classmate in Nigeria, who has married a high-flying solicitor. The food is served on self-consciously "ethnic" plates brought back from a holiday in India and Obinze is left wondering whether Emenike has become a person "who believed that something was beautiful because it was handmade by poor people in a foreign country, or whether he had simply learned to pretend so".

The polite conversation skates over race and the idea of foreignness, with each guest trying to outdo the next with their earnest political correctness. Adichie skewers their self-satisfaction with lethal accuracy. They "understood the fleeing from war, from the kind of poverty that crushed human souls", she writes. "They would not understand why people like him, who were raised well-fed and watered but mired in dissatisfaction, conditioned from birth to look towards somewhere else… were now resolved to do dangerous things, illegal things, so as to leave, none of them starving, or raped, or from burned villages, but merely hungry for choice and certainty."

In America, Ifemelu also finds it difficult to get part-time work. She gets turned away from menial jobs as a waitress, bartender or cashier. Her fellow students speak to her with painful slowness, as if she cannot comprehend basic English. In class, she is singled out as someone who will intuitively understand the plight of African Americans because of some half-formed belief in a nebulous, shared "black" consciousness.

Adichie is particularly good at exposing the contradictory ebb and flow of America's painful attempts to reconcile itself with its recent past, when segregation still persisted in the south. She does so with a wryness and insight that never imposes itself on the flow of the story but which challenges the reader's assumptions with each carefully crafted sentence.

There is the blond, well-heeled Kimberley who means well but says every black woman she sees is "beautiful", despite aesthetic evidence to the contrary. When Ifemelu buys a vintage 1960s dress on eBay she realises that when the original owner would have worn it, black Americans would not have been allowed to vote.

"And maybe," Ifemelu notes, "the original owner was one of those women, in the famous sepia photographs, standing by in hordes outside schools shouting 'Ape!' at young black children because they did not want them to go to school with their young white children."

Eventually, Ifemelu starts blogging about her experiences. Adichie captures the tone of internet chatter with precision – at once both breezy and sporadically furious – and the blogposts add an extra dimension to the plot, allowing the reader to see how Ifemelu sees herself and how she wishes to present herself to the outside world.

A recurring theme of the blogs is the politics of black hair – how women are expected to relax their natural curls with toxic chemicals or weave in bits of someone else's hair in order to conform to comfortable white norms. In fact, much of the novel is written in flashback, as Ifemelu has her hair braided in a New Jersey salon in preparation for going home to Nigeria after 15 years in America, during which she has witnessed Barack Obama's election victory.

The final section of the book follows Ifemelu's return and her reunion with Obinze who is, by now, married to someone else. It is to Adichie's immense credit that such a sprawling, epic book remains so tightly structured. There are, perhaps, one too many of Ifemelu's blogposts and a few extra scenes here and there that could have been cut, but part of Americanah's appeal is its immense, uncontained and beating heart. You can feel Adichie's passion and belief pumping beneath every paragraph.

Americanah is a deeply felt book, written with equal parts lyricism and erudition. More than that, it is an important book – and yet one that never lets its importance weigh down the need to tell a truly gripping human story.